Prosthetic joint replacement has become one of the most frequently performed elective surgical procedures but despite competent practices, can be complicated by failure either due to aseptic loosening or prosthetic joint infection (PJI). Current methods of laboratory diagnosis lack sensitivity and specificity with 7-39% of PJI cases being culture negative. Sonication of prosthetic components is an emerging technique aimed at optimising diagnostic sensitivity and specificity.
The ongoing study is aimed at evaluating the process and role of sonication of prosthetic orthopaedic devices, establish a protocol of collection, transport and processing of specimens, evaluate 16S rRNA PCR and sequencing in culture negative samples and to compare post sonication culture and 16S rRNA PCR with routine culture of peri-prosthetic tissues, intra operative swabs and synovial fluids.
All cases of proven or suspected prosthetic orthopaedic device infections where prosthetic components were removed and routine samples sent to ACT Pathology were included. The prosthetic materials collected during surgery in wide mouthed sterile containers were processed in the laboratory as per the method described by Trampuz et al.
Over a period of 15 months from March2014-May 2015, 42 prosthetic devices were processed from 32 patients and had accompanying 105 peri-prosthetic tissues/swabs/fluids for routine microbiology culture. Microbiological culture results post-sonication were compared with conventional culture. Microbiological diagnosis could be confirmed in 11 cases with both sonication and routine positive cultures. 7 additional cases could be identified on positive sonication culture results, where as in 3 patients routine cultures were positive but post-sonication cultures remained negative. All discordant results were evaluated on the basis of definition criteria and consensus agreement between the treating surgeons and ID physicians. Eleven patients remained culture negative by both methods and will be evaluated further by 16S rRNA PCR and sequencing.
Preliminary results indicate that post- sonication culture is possibly more sensitive than routine methods and the time to positivity is also substantially reduced in cases with concordant culture and sonication results. This could translate to quicker clinical decision making and management for potential patient benefit.